A novel glycosyltransferase organizes fungal glycogen and cell wall glucans

Abstract

Glycogen is a glucose storage molecule comprised of branched -1,4-glucan chains, best known as an energy reserve that can be broken down to fuel central metabolism. Because fungal cells have a specialized need for glucose in building cell wall glucans, we investigated whether glycogen is used for this process. For these studies we focused on the pathogenic yeast Cryptococcus neoformans, which causes over 112,000 deaths per year worldwide. We identified two enzymes that influence formation of both glycogen and the cell wall: Gly-cogenin (Glg1), which initiates glycogen synthesis, and a novel protein that we call Glucan organizing enzyme 1 (Goe1). We discovered that cells missing Glg1 lack -1,4-glucan in their walls, indicating that this material is derived from glycogen. Without Goe1, glycogen rosettes are mislocalized and {beta}-1,3-glucan in the cell wall is reduced. Altogether, our results provide mechanisms for a close association between glycogen and cell wall.